B4.1 - Ecosystems Flashcards
spec approved
What do arrows on a food chain show?
- the transfer of biomass
- transfer of energy
what is the difference between a food chain and a food web?
a food chain is a small section of the whole food web
what do food chains show?
the feeding relationship in an ecosystem
what are producers?
organisms that make their own food through photosynthesis
what are primary consumers?
animals that eat plants or algae (herbivores)
what are secondary consumers?
carnivores that eat herbivores
what is a tertiary consumer?
a carnivore that eats other carnivores
what are apex predators?
carnivores that have no other predators
what are decomposers
organisms that get energy from feeding on dead materials
what are consumers?
organisms that cannot make their own food and so have to eat other organisms
what are trophic levels?
each step in the food chain (where they feed)
what is a community?
organisms living within an ecosystem
define population
the total number of organisms of each species
what happens when an organism grows?
increases its biomass
state the factors affecting ecosystems and give a brief description
- biotic (living - beech trees, squirrels, hedgehogs)
- abiotic (nonliving - amount of rainfall, temperature of ecosystem)
what biotic factors affect communities? (4)
- food availability
- breeding partners
- COMPETITION
- new pathogens
how does light intensity affect communities?
- greater light available = greater plant success
- plants adapt for maximum absorption (larger leaves in low light)
how does temperature affect communities?
- affects enzymes controlling metabolic reactions
- plants develop faster
how does low moisture level affect plants?
- causes plants to wilt (low turgor pressure)
- water needed to keep cells turgid
- affects photosynthesis
what does the pH of soil affect?
- biological activity in soil
- availability of certain minerals
what kind of plants grow better in acidic soils?
ferns
what do plants need to survive? (5)
- light
- water
- carbon dioxide
- minerals
- space
what do animals need to survive? (5)
- food
- water
- breeding partner
- space
- shelter
define population
the number of organisms of each species living in an area
what is interdependence within a community?
how different organisms depend on each other
what are ecological relationships?
interactions between organisms
what are the three main types of ecological relationships
- predation
- mutualism
- parasitism
what is predation the relationship of?
- relationship between predator and prey
what is mutualistic relationship?
- both organisms benefit
give an example of a mutualistic relationship
bees taking pollen from plants
bees can make honey, plants become fertilised
what is a parasitism relationship?
one organism gains (parasite), other suffers (host)
give an example of a parasitism relationship
tapeworms in a human’s digestive system
what is commensalism?
one organism benefits from, but the other one is unaffected
what is an example of a commensalistic relationship?
tree frogs use plants as protection
what is a biotic factor?
a factor relating to animals (ie. competition of mating)
what is an abiotic factor?
a factor which is not living? (ie. rainfall)
why do food chains not exceed 4/5 tertiary levels?
not enough energy can be transferred to sustain life processes) - because of 10% rule
what does a pyramid of numbers show?
- the population at each trophic level (how many there are)
what do pyramid of numbers not take into account?
the size of the organism present
how do scientists calculate biomass?
- get dead organism
- dry the organism in a kiln (evaporate water mass)
- then measure it
CALLED DRY MASS
how do scientists calculate the total biomass at each trophic level?
measure average mass of each organism and multiply by the number of organisms present
state three reasons biomass is lost between trophic levels
- not all organism is eaten (animal bones/ plant roots)
- biomass is used during respiration
- some parts of organism cannot be digested (hair/teeth)
- released as waste products (excretion/ urine)
what is the nutrient cycle?
the process in which materials are passed between biotic and abiotic components of an ecosystem
what is carbon used to make?
GLUCOSE which makes…
- carbohydrates
- fat
- dna
- proteins
in what form can organisms use nitrogen?
when part of a compound (like a nitrate)
why do organisms use nitrogen?
- DNA
- proteins
Apart from providing water to organisms, describe another benefit of the water cycle
transports nutrients (helps replenish nutrients in different habitats)
how is carbon removed from the atmosphere?
- photosynthesis
how is carbon released back into the atmosphere? (3)
- respiration
- decomposition
- burning fossil fuels
how does the level of atmospheric carbon vary throughout 24 hours?
- decreases during daytime (photosynthesis)
- increases during nighttime (no photosynthesis, but respiration continues)
how do decomposers help the nutrient cycle?
release nutrients (can be recycled)
what are detritivores?
small animals which shred organic material to small pieces (create larger surface area for decomposers)
how do temperatures affect rate of decomposition?
- too high = enzymes used by microorganisms denature (they die)
- too low = rate of enzyme controlled reactions too slow
how does lack of water in environments affect rate of decomposition?
- not enough water = reactions slow down/stop
how does lack of oxygen affect decomposition?
decreases, oxygen needed for microorganism to respire (so cannot survive)
what is the equation to calculate the rate of decay of material?
rate of decay (g/day) = change in mass (g) / time (day)
give 3 examples of detritivores
- earthworm
- woodlouse
- maggot
what 3 factors affect rate of decomposition?
water level, temperature, oxygen level
difference between role of nitrogen-fixing bacteria and nitrifying bacteria (2)
- nitrifying turns ammonia to nitrates
- nitrogen-fixing turns nitrogen into nitrates
